2).While solving a problem, by mistake, Anita
squared a number and then subtracted 25 from it rather than first subtracting
25 from the number and then squaring it. But she got the right answer. What was
the given number?

6).In a farm there are cows and hens. If heads
are counted they are 180, if legs are counted they are 420.The number of cows
in the farm is ______.

a)130

b)150

c)50

d)30

Answer: d)

Explanation:
A cow and a hen each has a head.
If the total number of cows be x, then
Number of hens =180-x
A cow has four legs and a hen has two legs.
∴ (180 - x) × 2 + 4x = 420
→360 - 2x + 4x = 420
→2x =420 - 360 = 60
→x=60/2 =30

7).The number which can be written in the form
of n (n+1) (n+2), when n is a natural number, is _________.

a)7

b)3

c)5

d)6

Answer: d)

Explanation:
On putting n=1
N(n+1) (n+2) =1×2×3 =6

8).The value of (11111)2 is

a)12344321

b)121212121

c)123454321

d)11344311

Answer: c)

Explanation:
112 =121
1112 =12321
11112=1234321
111112=123454321

9).Two workers A and B are engaged to do a
piece of work. A working alone would take 8 hours more to complete the work
than when work together. If B worked alone, would take 4 ½ hours more than when
work together. The time required to finish the work together is _________.

a)5 hours

b)4 hours

c)8 hours

d)6 hours

Answer: d)

Explanation:
Time taken by A and B=x hours(let).
∴ According to the question, Time taken by A alone =(x+8) hours.
Time taken by B alone = (x+(9/2))hours.
∴1/(x+8) +1/(x+(9/2)) =1/x
→1/(x+8) +2/(2x+9) =1/x
→[2x+9+2x+16]/[(x+8)(2x+9)] =1/x
→[4x+25]/[2x2+16x+9x+72] =1/x
→4x2 +25x =2x2 +25x +72
→2x2 =72
→X2 =72/2 =36
→X=√36 =6 hours

10).If a man earns Rs.2000 for his first 50
hours of work in a week and is then paid one and a half times his regular
hourly rate for any additional hours, then the hours must he work to make
Rs.2300 in a week is ________.